Bus-duct and switch assembly



Oct. 24, 1944.

M. J. DE MASK BUS-DUCT AND SWITCH ASSEMBLY Filed Jan. 24, 1941 4 Sheets-Sheet 1 //v vs/v 7-0;? Mar/#7 J De/Vaak 4 7' TOP/V5 Y Oct. 24, 1944. J DE MASK 2,361,179

BUS-DUCT AND SWITCH ASSEMBLY Filed Jan. :24, 1941 4 Sheets-Sheet 2 ,4 7" TOP/V5 Y Oct. 24, 1944.

M. J. DE MASK Filed Jan. 24, 1941 BUS-DUCT AND SWITCH ASSEMBLY 4 Sheets-Sheet 3 //v l/EN 701-? 0.7 Mar/9)? Jae/705% ATTORNEY j Oct. 2-4, 1944. DE MASK 2,361,179

BUS-DUCT AND SWITCH ASSEMBLY A 7' TQRNE Patented Oct. 24, 1944 BUS-DUCT AND SWITCH ASSEMBLY Martin J. De Mask, Pittsfield, Mass., assignor to The Trumbull Electric Manufacturing Company, Plainville, Con-11., a corporation of Connecticut Application January 24, 1941, Serial No. 375,743

Claims.

My invention particularly relates to a novel form of bus duct or duct within which bus bars are adapted to be supported, and to a power take-01f unit for use with bus ducts.

, one current carrying part of the system to another. Arcing, of course, may occur between the switch blade and the contacts engaged thereby and also between the bus bar-engaging contacts.

and the bus bars.

It is an object of my invention to provide a power take-off unit which may be readily applied to a bus duct and electrically connected with the bus bars therewithin and which is so arranged that arcing occurring at either the bus bar-engaging contacts or the switch blade-engaging contacts thereof cannot 'pass from one to the other of said contacts or conductors associated therewith.

Another object resides in providing a power take-off unit of the foregoing character comprising a body of electrical insulating material provided with recesses on one side thereof adapted to receive bus bars therewithin and having electrical contact means disposed within the said recesses and adapted to engage said bus bars, said body being provided with barrier means extending laterally of said recesses and on opposite sides of the bus bars when said bus bars are disposed therewithin, and on opposite sides of the bus bar-engaging contacts mounted with said recesses. Another object resides in providing a power takeoff unit comprising a body of the foregoing character in which the barriers are disposed on opposite sides of the bus bar-engaging contacts and in substantially closely spaced relation thereto.

Another object of my invention resides in providing a power take--oif unit, adapted to prevent arcing between the switch blades thereof, between the switch blades and bus bars or between the contacts adapted to engage the bus bars and those adapted to be engaged by the switch blades, which comprises a body of electrical insulating material having insulating means forming recesses in one side thereof, contact means disposed Within said recesses and adapted to be engaged by switch blades, and contact means disposed on the other side of said insulating body which are adapted to engage the bus bars within a duct. Another object resides in providing a body of insulating material of the foregoing character with insulating means for effecting a closure of both ends of said recesses therein. Other objects reside in providing power take-off units of the foregoing character in which insulating means are provided to overlie the said recesses therein and to form substantially a closure therefor but providing openings through which operating levers, connected to the switch blades, may pass and branch circuit connections may be made to the take-off unit; in which the recesses are designed to permit a movable switch blade and a fuse and fuse clips to be mounted therein and in which an insulating barrier subdivides said recesses into compartments for the switch blade and for the fuse and fuse clips, respectively.

Another object of my invention resides in providing a cover for the opening in the bus duct through which the power take-off unit is adapted to be inserted, said cover comprising two, separable portions and one of said portions being secured to the bus duct and including a wall adapted to have a conduit for the branch circuit conductors to be secured thereto; the two portions of said cover together forming a substantial closure for said opening in the bus duct.

Still another object of my invention resides in 0 providing a bus duct structure comprising a generally plate-like element to which channel-like members may be fastened on one or both sides thereof, said plate-like element being adapted to have supporting means attached thereto and so to support said channel-like members that they may be removed from said element while it is so supported.

I attain the foregoing objects of my invention by the novel arrangements and correlation of elements described below and illustrated in the accompanying drawings in which Fig. 1 is a sectional elevation view taken transversely of a bus duct in about the plane I-l of Fig. 2, showing one form of power take-off unit mounted therein;

Fig. 2 is a fragmentary, sectional elevation view taken longitudinally of the duct and in about the plane 22 of Fig. 1;

Fig. 3 is a fragmentary, sectional elevation,

iew, somewhat similar to Fig. 1, but showing a modified structure;

4 is a fragmentary, plan view of the insulating body of a preferred form of power take off unit;

Fig. 5 is a fragmentary perspective view of the insulatin body showing barrier means applied thereto;

Fig. 6 is a fragmentary, sectional elevation view taken longitudinally through the body of Fig. 4 and showing the barrier means of Fig. 5 afiixed thereto;

Fig. 7 is a fragmentary, sectional view in perspective further illustrating the barrier means of Fig. 5 positioned on the insulating body;

Fig. 8 is a bottom plan view of the insulating body showing a cover plate applied thereto;

Fig. 9 is a sectional elevation view taken 1ongi tudinally of a modified form of insulatin body;

Fig. 10 is a fragmentary, sectional elevation view taken longitudinally of a bus duct and a modified form of insulating body of a power takeoff unit mounted therein and showing a modified cover plate afiixed to said insulating body;

Fig. 11 is an end elevation view of the cover plate shown in Fig. 10;

Fig. 12 is a sectional elevation view taken transversely of a bus duct showing a modified form of power take-off unit applied thereto;

Fig. 13 is a fragmentary, sectional elevation view of the structure of Fig. 1.2 taken in about the plane I3I3' thereof;

Fig. 14 is a fragmentary, perspective view of the plate-like element and associated angle pieces of the duct structure of Fig. 12;

Fig. 15 is a perspective view of the insulating body of the power take-on unit shown in Figs. 12 and 13; and

Fig. 16 is an elevation view of a cover plate designed to be affixed to one end of the insulating body of Fig. 15.

It will be understood that the bus duct, herein illustrated and described, may be made up of sections, in the customary manner, which are joined end to end to form a continuous bus duct. I have herein illustrated but a small portion of a bus duct but sufficient thereof to show the manner in which the power take-01f unit may be applied thereto. Furthermore, it will be understood that although I have not illustrated supports for the bus bars in some of the figures, the bus bars may be supported in any customary manner such as by spring hangers or, in accordance with my invention, preferably on brackets which may be secured as illustrated in Fig. 13 to the bottom of the duct. In the embodiment illustrated, the bottom of the duct comprises a plate-like element to which the casings are secured.

Referring to the drawings, I indicates generally a bus duct which comprises a generally channel shaped casing 2, adapted to extend about the bus bars 3 and to be fastened to and supported upon a generally plate-like element 4. For purposes of illustration, I have shown three bus bars. In the embodiment illustrated, angle irons 5 and 6 are fastened to opposite side edges of the plate 4. Casing 2 is fastened to the angle iron 5 by means of screws I and it will be observed that the plate 4 and casing 2 form a closure within which the bus bars 3 extend in spaced relation to the duct and to each other.

In the zone where it is desirable to provide a power take-off unit, the plate 4 is provided therein with an aperture 8 of sufiicient size to permit the unit to be inserted therethrough. The power take-off unit of this invention comprises, in its preferred form, a body 9 of electrical insulating material which is provided in one side thereof with recesses I0 adapted to receive the bus bars therein and in the other side with recesses II in which are mounted contacts I2 of electrical conducting material which are adapted to be engaged respectively by switch blades I3. The contacts I2 are preferably of the usual form comprising a pair of resilient, electrical conducting arms adapted to be spread apart and closely to engage a switch blade when it is moved therebetween. In each recess II, the switch blade I3 is pivotally supported as indicated at I4 on a bracket I5 of conducting material which is electrically connected with one clip I6 of a pair of fuse clips I6 and II. A fuse I8 is illustrated mounted in said clips, and clip I! is electrically connected with a binding post or terminal I9 to which branch circuit conductors 20, as shown in Fig. 2, may be connected. The conductors 20, of course, are respectively connected to the binding posts in the various recesses II of the insulatin body.

For operating the switch blades I3, operating levers or links 2I are pivotally connected as at 22 to each of said switch arms and are in turn fastened to a common arm 23. Arm 23 comprises a shaft 24 which, in the embodiment illustrated, is resiliently coupled to a ring 25 by means of which an operator may actuate the switches. The coupling 26 comprises a casing 21 which is connected to ring 25 and within which the end of shaft 24 may reciprocate. A shoulder 28 is provided on the end of shaft 24 and a helical spring 29 is interposed between said shoulder and a cap 30 which is screw threaded on the end of the casing 21. A resilient coupling of this character enables an operator to effect a rapid opening of the circuit between the switch blades and the contacts engaged thereby.

Contacts 3I of electrical conducting material are mounted within the respective recesses ID of the body 9 and are adapted to engage the bus bars 3. These contacts are preferably of a construction generally similar to contacts I2 and are electrically connected therewith by means of straps 32 which, in each case, extend through the insulating walls of the body 9 and in electrical contact with the contacts I2 and 3|, respectively.

The insulating body 9 is provided with lugs 33 preferably adjacent both side edges and at opposite ends thereof. When the insulating body is inserted within the casing 2 as shown in Fig. 1, the lugs 33 are adapted to engage the under sides of brackets 34 which are secured preferably to the plate 4 in any suitable manner as by screws. Wing screws 35 are then passed through openings in the lugs 33 and screw threaded into the brackets 34 to hold the insulating body securely in position within the duct.

Tie rods 36 which may be anchored to a celling and are designed to support the bus duct may be passed through openings which lie adjacent the side edges of the plate 4 and extend through the angle irons 5 and 6, nuts 31 and 33 being threaded on the ends of said rods securely to fasten them to the bus duct. With a bus duct construction of this character, it will be observed that the plate 4 is supported in zones thereof disposed laterally beyond the casing 2 and, therefore, while the duct is so supported, screws I may be loosened sufiiciently to permit casin 2 to be removed for any purpose without necessitating the removal or disturbance in any way of the other parts of the duct or power take-off unit.

In eifecting a closure of the aperture 8 in plate 4, I prefer to employ a casing 39 comprising two portions 40 and 4|. The portion 40 of the casing is secured to plate 4 or may be secured, of course, to angle irons 6 and comprises a wall or walls towhich a branch circuit conduit may be secured. As'illustrated in Fig. 2, conduit 42 is secured to the portion 40 of casing 39 by means of the usual locknut and bushing and knock-outs such as indicated at 43| may also be provided in the portion 40. The portion 4| of this casing is preferably fastened at one end, as by screws 43, to or pivoted on the portion 40 and the other end thereof may be secured to the angle irons 6 or to the plate 4, as illustrated, An opening 44 is provided in the portion 4| of casing 39 through which the shaft 24 of the operatin arm for the I switch blades l3 may pass.

The portion 45 of casing 39 is so positioned relative to aperture 8 in plate 4 as to permit body 9 of the take-off unit to be readily inserted or Withdrawn through said aperture, when it,

is exposed, and it will be noted that this may be accomplished without disturbing the conduit It will be observed that in the embodiment of the insulating body 9 shown in Figs. 1 and 2 both ends of the recesses H are closed by electrical insulating material as indicated at 54 and both ends of the recesses II] are preferably partially closed by means of barriers 4-5 which extend inwardly on both sides of the bus bars 3 when disposed therein and into close proximity to the sides of the bus bars. With this arrangement, the travel in a direction longitudinally of the bus duct of any are occurring at the surface of the bus bars or between switch blades and contacts is prevented to a great extent.

In Fig. 3, I have shown a somewhat modified form of insulating body for the power take-off unit. 'In this modification, the duct structure is substantially the same as that above described bars or, in other words, to provide as much in-- sulating space as possible directly between the bus bars and conductors electrically connected therewith of different polarities. Furthermore, with this construction, the parts of the take-off unit lie well Within the casing 2 so that the casing 4| may be relatively shallow providing a more uniform size of duct structure throughout its length.

As hereinabove described, the body 9 of the insulating material is provided with barriers 45 adjacent both ends of the recesses Ill therein as clearly shown in Fig. 4. However, in order still further to confine any arcing, which may occur. to those zones wherein the bus bars are engaged by the contacts of the take-off unit, I prefer to provide barrier means which lie on both sides of the bus bars and on opposite sides and in fairly closely spaced relationship to the contacts adapted to engage the bus bars; and alsobarrier means extending across the recesses H! of the insulating ISO body and above the bus bar-engaging contacts therein. The preferred construction is illustrated in Figs. 5, 6 and 7. An angle member 46 of electrical insulating material, comprising what may be termed an end plate 41 and top plate 48 is fastened to the end of the body 9 adjacent which is mounted the bus bar-engaging contacts -3l. The upper edges of the ribs of body 9 may be 'rabbeted as indicated at 49 to receive the top plate 48 of member 46 and the end plate 41 thereof is adapted to abut the end of the body 9. These parts may be fastened together b means of screws 50 as illustrated. The top and end plates of the member 46 are provided with slots 51 which are of sufiicient width to permit the bus bars to pass therethrough and, preferably, the bottom of these slots in the end plate 45 lie closely adjacent the bottom of the bus bars when the body 9 is operatively positioned in the duct. The top plate 48, adjacent the end thereof remote from the end plate 41, is provided with baffle members 52 which extend downwardly within the recesses ll) of the body at least substantially to the bottom of the bus bars when operatively positioned therein and also extend from the sides of the recesses toward the bus bars, preferably terminating substantially in the planes of the sides of the slots 5| and closely adjacent the sides of the bus bars.

When using a member of the character of member 46, above described, in connection with the insulating body 9, it is, of course, not necessary to provide the said body with the barriers 45 at the ends of the recesses l0 therein. However, it will be noted that the barriers formed by member 46, being disposed above and on opposite sides of the bus bar-engaging contacts, will to a very great extent confine any arcing occurring between the contacts and bus bars to the zone wherein it originates.

It is also desirable, as hereinbefore pointed out, to confine any arcing occurring between the switch blades and their associatedcontacts to a zone within the recesses I! of the insulating body 9; and it is'alsc desirable to prevent such arcing from travelling to the fuses or fuse clips within these recesses. Therefore, I preferably provide a plate of insulating material as illustrated in Figs. 8 to 11, inclusive. which is adapted to overlie the recesses H and to confine arcing to these recesses. 'As illustrated in Fig. 8, I may provide a plate 53 or electrical insulating material which is secured to the base of the body 9 and overlies the recesses i! therein. the plate extending between the ends 54 of the body 9 which form closures for the ends of the recesses H and substantially entirely enclosing the electrical conducting parts within said recesses. The plate 53, however, is provided with openings or slots 55 through which the operating levers 2| for the switch blades may pass. The plate 53 may be removably secured to the body 9 by means of screws 56. Plate 53 is also preferably provided with slots 56l through which the branch circuit conductors may pass for connection to the binding posts within the recesses l l.

In Fig. 9. I have illustrated a somewhat modified form of insulating body 9 and base plate for partially enclosing the recesses ll therein. In this embodiment. a partition 5! of insulating material extends between the sides of the recesses I l and preferably from. the top to the bottoms thereof. This partition subdivides the recesses into a compartment for the switch blade and its associated contact and a compartment for the fuse clips, fuses and binding posts. One of the fuse clips, of course, is electrically connected with the switch blade by means of a strap 58 which extends through the partition 51. A plate 59 of electrical insulating material is fastened to body 9 as by screws 60 and efiects a substantial closure of the compartments housing the switch blades and their associated contacts. Slots GI, similar to the slots 55 shown in Fig. 8, are provided in the plate 59 through which the operat-, ing levers 2I for the switch blades may pass. It will be observed that in this embodiment of my invention, any arcing occurring between the switch blades and their associated contacts is confined to the compartment housing the same and such arcing cannot travel to the fuses or fuse clips.

In Fig. 10, I have illustrated a further modified construction of the insulating body 9 and cover plate therefor. In this embodiment, the ends of the recesses II in the insulating body, adjacent the binding posts therein, are open. A cover plate of electrical insulating material for enclosing the recesses I I is indicated generally at 62 and comprises a base plate 63, which may be similar to the plate 53, and an end plate 64 which is adapted to overlie the end of the insulating body 9 and form a partial closure for the open end of the recesses I I therein. Fig. 11 clearly illustrates the construction of the end plate 64. The base plate 63, which may be similar in most respects to plate 53, above described, is provided with slots 65 through which the operating levers for the switch blades may pass, and the end plate 64 of the cover plate 62 is provided with slots 65 through which the bus bars are adapted to extend and slots 61 which are adapted to register with the ends of the recesses I I and permit the branch circuit conductors to extend therethrough when connected to the binding posts of the take-off unit. Slots 68 extending inwardly from opposite sides of the plate 64 are provided to enable plate 64 to be positioned over the lugs 33 of the insulating body 9. The cover plate 62 may be fastened to the body 9 by means of screws 69 as shown. Of course, in this latter embodiment of my invention, the end plate 64 forms a barrier for one end of the recesses I through which the bus bars extend and therefore the barriers 45 at the end of said recesses adjacent which the plate 64 is adapted to lie are not necessary.

The embodiment of my invention illustrated in Figs. 12 through 15. inclusive, comprises a power take-off unit which is illustrated as applied to a duct of the general character illustrated in Figs. 1 and 2. This duct comprises a plate-like element 4 to which is fastened casing 2 extending about the bus bars 3 and to which, on the other side thereof, is secured a second casing 70 on which is preferably supported the power take-oil unit. As in the first described embodiment of my invention, tie rods 36 are adapted to be secured to the plate 4; and angle irons 5 and 6, to which the casings 2 and I0, respectively, may be fastened, are preferably secured to the plate 4.

It will be understood that while casings, or covers, 2 and 'IG are usually co-extensive with plate 4, they may be of any desired length. Furthermore, adjacent casings, or covers, 2 and I0 may be supported in spaced relation to-each other to provide an opening in the respective ducts through which a power or electrical take-oil? unit may be inserted into operative relation to the bus bars or bus runs. Hence, the term aperture as used herein and in the appended claims is intended to include an opening formed in this manner. It will also be understood that the casings, or covers, 2 and I0 might be removed to permit the placing of an electrical take-oft unit in operative relation to the bus bars or bus runs and that after the unit had been so placed the covers would be replaced.

As illustrated in Fig. 13, the bus bars 3 are supported on brackets II which are mounted on plate 4 and are insulated therefrom by insulating blocks I2.

In this embodiment of my invention, the plate 4, as illustrated in Fig. 14, is provided with apertures I3 illustrated as three in number since it is assumed that there are three bus bars within the duct. Obviously, a single opening could be used instead of a plurality thereof through which the bus bar-engaging contacts could be inserted into the duct and into operative relation to the bus bars therein. The bus bar-engaging contacts of the power take-oil unit are adapted to be passed through the apertures I3, as hereinafter described, and into engagement with the respective bus bars.

The casing 10 is provided with an aperture H through which the power take-off unit is adapted to be inserted. The power take-off unit, in the embodiment illustrated, comprises a base I5 preferably of electrical insulating material on which is mounted a body of insulating material 16. The body 15 comprises sides I1 and a top 18. The top and sides may be formed integral or fastened together. The body also is provided with partitioning elements 19 which extend longitudinally thereof and subdivide the interior of the body into three recesses or longitudinally extending passages. As illustrated in Figs. 12 and 13, fuse clips are mounted in each of these passages, one of said clips being electrically connected with a binding post BI and the other there of being electrically connected with the support for a pivotally mounted switch blade 82. A fuse 83 is illustrated as mounted in the fuse clips. Contacts 84, which are adapted to be engaged by the respective switch blades, are secured to the top I8 of the take-oif unit and are electrically connected, respectively, with contacts 85 which are secured to the upper surface of the top of the unit. Contacts 85 are adapted to engage the bus bars 3 when the unit is operatively positioned within the casing I0.

Barrier means 86 of electrical insulating material are provided for each of the contacts 85 and these barrier means, respectively, are adapted to be inserted together with the contacts through the apertures I3 in the plate-like element 4 of the duct structure. ment illustrated, the barriers 86 comprise hollow, body portions approximating elliptical prisms in shape, although other configurations may be used, which upstand from the top I8 of the insulating body and are provided with upper ends 81. The contacts 85 are disposed within the barriers, and the barriers are provided with slots 88 extending through the ends 81 thereof and lengthwise of the bodies to a sufficient depth to permit the bus bars to pass within said slots and engage the contacts 85 when the take-01f unit is fastened in position on the duct.

The partitioning elements I9 are preferably partially cut away as indictaed at 89 to provide for movement of the arm 90 to which the switchoperating levers are connected. The base I5 is provided with an opening SI through which the In the embodishaft 92 of the operating arm '99 may pass.

The side members 11 of the body 16 are preferably provided with threaded openings 93 therein to permit an insulating plate 94 (see Fig. 13) to be fastened by means of screws thereto to effect a closure of the end of the body 16 adjacent the contacts 84. A similar plate, as indicated at 95 in Fig. 16, is adapted to be fastened by means of screws to the opposite end of the body 16 and is provided with slots 96 through which the branch circuit conductors may extend when connected with the respective binding posts 8| of the unit.

It will be observed that the closure plates 94 and 95 cannot be removed when the power takeoff unit is in operative position and therefore that access to the fuses 83 or switch blades 82 may be had only by removing the take-off unit from the casing, or cover, 10, in which position there is no current-carrying or live parts on the take-off unit and consequently no danger to anyone inspecting or servicing the unit.

The power take-oil unit of this embodiment of my invention, when operatively applied to a bus duct, is inserted through the aperture 14 in the casing with the barriers 86 also passing through the apertures 13 in the plate-like element 4. When the contacts 85 properly engage the bus bars 3, the base '15 of the take-off unit will lie adjacent the bottom of the casing 10 and may be secured thereto by means of wing screws 91 which pass through openings in the base 15 and are threaded into the casing ll). Prefer- .ably, the casing 19 is provided with knock-outs may be provided at spaced intervals along the duct structure and that apertures 74 may likewise be provided in casing 10 so that take-oil units may be applied to the bus runs in said duct at desired points. It will also be under-. stood that apertures 8 and 13, and likewise aperture 14, may be closed when not in use by fiat closure plates in a manner well understood in the art.

It will be observed that the above described power take-oil" unit effectively insulates the switch blades and their associated contacts and fuses from the bus bar-engaging contacts and may be readily mounted on the bus duct or removed therefrom. Furthermore, the casing 2 may be removed for bus bar inspection or other purposes, if desired, while the duct is supported on the tie rods 36 without necessitating the removal of the power take-01f unit.

It will be understood that the fuse clips, contacts and other current carrying parts of my power take-off units may be secured in any desired manner to inserts which are molded in the insulating bodies as shown in dotted lines or they may be secured in position in any other desired manner.

Furthermore, although I have illustrated three bus bars, switch blades and associated contacts, the numbers thereof may be varied. Moreover, casings 10 may be supplied throughout a bus duct run or provided only in those zones where true scope and spirit of my invention in its broader aspects.

What I claim is:

1. In a device of the character described, a duct provided with an aperture therein, bus bars supported within said duct and electrically insulated from each other and a power take-off unit adapted to be inserted through said aperture into said duct; said unit comprising a body of electrical insulating material provided with generally parallel, spaced recesses in a first side thereof adapted to receive said bus bars therewithln and generally parallel, spaced recesses in a second side thereof oppositeto said first side, and electrical contact means disposed in said recesses, the contact means in the recesses of said first side being adapted to engage said bus bars and being permanently, electrically connected respectively with the contact means in the recesses in said second side and said latter contact means being adapted to be engaged bya switch blade; and said body being provided with means forming barrier elements extending transversely of said first mentioned recesses therein and from opposite sides thereof into close proximity to the bus bars when disposed Within said recesses.

2. In a device of the character described, -a

duct provided with an aperture therein, bus bars supported within said duct and electrically insulated from each other and a power take-off unit adapted to be inserted through said aperture into said duct; said unit comprising a body of electrical insulatingmaterial provided with generally parallel, spaced recesses in a first side thereof adapted to receive said bus bars therewithin and generally parallel, spaced recesses in a second side thereof opposite to said first side, and electrical contact means disposed in said recesses, the contact means in the recesses of said first side being adapted to engage said bus bars and being permanently, electrically connected respectively with the contact means in the recesses in said second side and said latter contact means bein adapted to be engaged by a switch blade; and said body being provided with an element comprising barrier means of electrical insulating material extending transversely of and from opposite sides of said first mentioned recesses therein into close proximity to the bus bars when disposed within said recesses, said barrier mean being relatively spaced longitudinally of said recesses but in closely spaced relation to and on opposite sides of the contact means therewithin.

3. In an electrical duct system of the character described, a plate-like element, a pair of generally channel-shaped casings supported on opposite sides of said element, a plurality of bus bars supported within a first of said casings in spaced relation to each other and said casing, said element extending laterally beyond said first casing, and means adapted to be secured adjacent the side edges of said element for supporting the same; whereby said first casing may be removed from said element to expose said bus bars while said element is supported by said means,

4. In an electrical duct system of the character described, a plate-like element, a generally channel-shaped casing supported on one side of said element, and a plurality of bus bars supported within said casing in spaced relation to each other and said casing, said element extending laterally beyond the sides of said casing whereby supporting rods may be fastened to said element and, while said element is so supported, said casing may be removed therefrom, said plate-like element having an aperture therein, a power takeoff unit adapted to be inserted through said aperture and comprising a body of electrical insulating material having insulating means forming a recess in one side thereof, electrical contact means adapted to be engaged by a switch blade disposed within said recess, a switch blade movably supported on said body and Within said recess, and contact means adapted to engage said bus bars being mounted on the side opposite to the first mentioned side of said body and being electrically connected with said first mentioned contact means, and a second, generally channel-shaped casing supported on said plate-like element and on the side thereof opposite to said first mentioned channel-shaped casing, said second casing being provided with an aperture through which said take-ofi unit may be inserted, and means for fastening said unit to said second casing.

5. In a device of the character described, a duct provided with an aperture therein, bus bars supported within said duct and electrically insulated from each other and a power take-off unit adapted to be inserted through said aperture into said duct and into operative relation to said bus bars; said unit comprising electrical insulating material formed to provide recesses on opposite sides of said unit, the recess on one side of said unit lying between the recesses on the opposite side, a first electrical contact means disposed within a recess on one side, a switch blade coacting therewith and a second contact means disposed in a recess on the opposite side of said unit being electrically connected to said first contact means and adapted to engage a bus bar.

6. In a device of the character described, a duct provided with an aperture therein, bus bars supported within said duct and electrically insulated from each other and a power take-01f unit adapted to be inserted through said aperture into said duct and into operative relation to said bus bars; said unit comprising electrical insulating material formed to provide a recess on one side of said unit, a first electrical contact means disposed within said recess, a switch blade coacting with said contact in said recess and a second contact means mounted on said unit and adapted to engage a bus bar, said first and second contact means being electrically connected together, and said recess being disposed between a bus bar and an adjacent side of said duct when said unit is inserted through said aperture and into operative relation to a bus bar within said duct.

'7. In a bus duct electrical distribution system,

a duct, parallel bus bars therein, an insulating block transversely disposed in said duct having grooves in one face thereof with contacts to engage the bus bars from below and having recesses in the opposite face and in the same transverse plane as said grooves, and a switch in each of the latter recesses, each switch having a terminal connected to one of the contacts in said grooves and a terminal in each of said recesses for a branch conductor, all within the duct.

8. A duct, bus bars in said duct, an insulating block transversely and entirely disposed in said duct and having spaced recesses opening in opposite directions and positioned in the same transverse plane; contacts accessible upwardly in alternate recesses and adapted to engage said bus bars, contacts accessible downwardly in the other recesses and switch blades in said latter recesses movable into and out of engagement with the latter contacts, said block, contacts and blades forming a removable unitary structure.

9. A power take-01f device for a bus bar duct comprising an insulating body portion having a series of spaced recessed chambers transversely arranged in alignment and alternately opened upwardly and downwardly; an upwardly exposed contact in each of the upwardly opened chambers for engaging a bus bar; a downwardly exposed contact in each of the downwardly opened chambers; means for operatively connecting said upwardly and downwardly exposed contacts; a movable switch member in each of the downwardly opened chambers; all of said contacts and movable switch members being positioned in substantially the same transverse plane; and a downwardly extending member connected to the movable switch members for moving same into and out of engagement with the downwardly exposed contacts; all of said parts forming a unitary structure.

10. A branch connector device for attachment to a bus bar duct comprising an insulating body having a number of parallel channels arranged in a row extending transversely of the body, alternate channels being open toward opposite faces of the body and separated from each other by insulating walls, exposed contacts mounted in the respective channels, the contacts exposed at one face being adapted to engage bus bars, mov- 50 able switch members mounted to engage the contacts in the channels in the opposite face of the body and conducting strips extending through said walls and connecting the contacts in the respective channels.

MARTIN J. DE MASK. 

